1. Field of the Disclosure
This disclosure relates to an apparatus and method that optimizes feedable sheet availability in a feed tray of a feeder module.
2. Description of Related Art
As shown in FIG. 1 of U.S. Pat. No. 7,900,906 B2, the contents of which are included herein by reference, feeding of media sheets in present day copiers and printers include a scheduler and media sheet source, as well as, a marking engine and media sheet stacker. In a marking engine, such as a xerographic marking engine, a photoconductive insulating member is charged to a uniform potential and thereafter exposed to a light image of an original document to be reproduced. The exposure discharges the photoconductive insulating surface in exposed or background areas and creates an electrostatic latent image on the member, which corresponds to the image areas contained within a document. Subsequently, the electrostatic latent image on the photoconductive insulating surface is made visible by developing the image with a developing material. Generally, the developing material comprises toner particles adhering triboelectrically to carrier granules. The developed image is subsequently transferred to a sheet of media, such as a sheet of paper, a transparency, or other sheet of media, that is fed from a media sheet source. A stacker can then stack the marked media sheets. A scheduler can schedule feed commitments for a number of sheets to be fed by the media source, marked by the marking engine, and stacked by the stacker. For example, the scheduler can inform each element that a certain number of sheets will be processed by the elements. As one of the scheduled elements, a media sheet source must plan and commit to a variable number of feed commitments.
Unfortunately, feedable capacity of the media sheet source may not be sufficient to satisfy outstanding feed commitments scheduled by the scheduler. For example, the media sheet source fed tray may not contain enough media sheets to meet the outstanding feed commitments. An unscheduled shutdown or jam can result from the media sheet source attempting to feed sheets after the feed tray is empty. Attempting to feed sheets after the feed tray is empty can also result in damage to the media sheet source. Furthermore, other elements, such as, the marking engine and the stacker can be damaged if they attempt to process scheduled, but unfed sheets. This can occur when a media sheet source cannot adequately control its feed commitments based on it feedable capacity and will stop feeding sheets even though the feed tray is not empty.
Additionally, due to the scheduling mechanism applied in a current machine, it is possible for the print engine to schedule as many as 50 sheets ahead. In order to compensate for this without declaring a fault, the feeder tray must declare low paper early enough to compensate for these outstanding commitments. Currently, as disclosed in heretofore mentioned U.S. Pat. No. 7,900,906 B2, this is done based on an assumption of average sheet thickness and number of outstanding commitments. When this approach results in an early declaration of low paper, more paper is left in the feeder tray. When the low paper declaration occurs too late, the feeder tray can reach its upper travel limit, and misfeeds can occur.
Thus, there is still a need for a method and apparatus that can reliably control feed commitments.